Is this click fraud for Cubics.com traffic?

Buy Targeted Ads on Social NetworksCubics is the first and only advertising network that allows advertisers to target users of social networks such as FacebookTM, MySpaceTM, Friendster & Bebo.
So I bought a 'test' amount of pre-paid credits to run some banner ads for one of the Live Fan Chat website http://www.LiveBaseballChat.com

Pretty straight forward and uses the same text we use for our google text ads. We've tried a few different variations and generally get a few clicks each and every day at a very dependable rate (it's a pretty niche target market + we have a very small limit set for our daily budget).
So for the first few days with Cubics it looked like we were getting the same reliable click through numbers each day and looked like our $20 test investment would last about a week, until today.

I just got an email a few hours ago saying my account had been depleted and i needed to add more credits or the campaign will be cancelled.

Then when I realised every single visitor only visited 1 page and then logged off in less than 10 seconds.

Then when i checked google analytics I found out all of the visits occurred within a 1 hour period...... (9pm est).

hmmmm -

Does http://www.cubics.com/ have a problem with click fraud or were they just very lucky displaying my advertisement to 198 people who clicked on then left without clicking any links onto other pages all in a 1 hour period.